Grüss, A., Kaplan, D. M., and Robinson, J. Evaluation of the effectiveness of marine reserves for transient spawning aggregations in data-limited situations. â€“ ICES Journal of Marine Science, doi:10.1093/icesjms/fst028. Many coral reef fish species form predictable, transient spawning aggregations. Many aggregations are overfished, making them a target for spatial management. Here, we develop a per-recruit model to evaluate the performance of no-take marine reserves protecting transient spawning aggregations. The model consists of only 14 demographic and exploitation-related parameters. We applied the model to a protogynous grouper and a gonochoristic rabbitfish from Seychelles and tested six scenarios regarding the extent of protected areas, the level of fish spawning-site fidelity, and fishing effort redistribution post reserve implementation. Spawning aggregation reserves improve spawning-stock biomass-per-recruit and reduce the sex ratio bias in protogynous populations for all scenarios examined. However, these benefits are often small and vary among the different scenarios and as a function of sexual ontogeny. In all scenarios, increases in yield-per-recruit do not occur or are negligible. The long-term yield increases due to spawning aggregation reserves may still occur, but only if spawning-stock biomass recovery results in a recruitment subsidy. Given these limited benefits, the value of no-take reserves must be weighed against those of other management options, such as fishing effort reduction and seasonal fishery closures. The latter is particularly appropriate when spawning and non-spawning areas overlap in space.

AimAssessing the spatial structure and dynamics of marine populations is still a major challenge in ecology. The need to manage marine resources from ecosystem and large-scale perspectives is recognized, but our partial understanding of oceanic connectivity limits the implementation of globally pertinent conservation planning. Based on a biophysical model for the entire Mediterranean Sea, this study takes an ecosystem approach to connectivity and provides a systematic characterization of broad-scale larval dispersal patterns. It builds on our knowledge of population dynamics and discusses the ecological and management implications. LocationThe semi-enclosed Mediterranean Sea and its marine ecosystems are used as a case study to investigate broad-scale connectivity patterns and to relate them to oceanography and population dynamics. MethodsA flow network is constructed by evenly subdividing the basin into sub-regions which are interconnected through the transport of larvae by ocean currents. It allows for the computation of various connectivity metrics required to evaluate larval retention and exchange. ResultsOur basin-scale model predicts that retention processes are weak in the open ocean while they are significant in the coastal ocean and are favoured along certain coastlines due to specific oceanographic features. Moreover, we show that wind-driven divergent (convergent, respectively) oceanic regions are systematically characterized by larval sources (sinks, respectively). Finally, although these connectivity metrics have often been studied separately in the literature, we demonstrate they are interrelated under particular conditions. Their integrated analysis facilitates the appraisal of population dynamics, informing both genetic and demographic connectivities. Main conclusionsThis modelling framework helps ecologists and geneticists to formulate improved hypotheses of population structures and gene flow patterns and to design their sampling strategy accordingly. It is also useful in the implementation and assessment of future protection strategies, such as coastal and offshore marine reserves, by accounting for large-scale dispersal patterns, a missing component of current ecosystem management.

Patellogastropods, also known as true limpets, are distributed throughout the world and constitute key species in coastal ecosystems. Some limpet species achieve remarkable sizes, which in the most extreme cases can surpass 35 cm in shell length. In this review, we focus on giant limpets, which are defined as those with a maximum shell size surpassing 10 cm. According to the scientific literature, there are a total of 14 species across five genera that reach these larger sizes. Four of these species are threatened or in danger of extinction. Inhabiting the intertidal zones, limpets are frequently affected by anthropogenic impacts, namely collection by humans, pollution and habitat fragmentation. In the case of larger species, their conspicuous size has made them especially prone to human collection since prehistoric times. Size is not phylogeny-dependent among giant limpets, but is instead related to behavioural traits instead. Larger-sized species tend to be nonmigratory and territorial compared to those that are smaller. Collection by humans has been cited as the main cause behind the decline and/or extinction of giant limpet populations. Their conspicuously large size makes them the preferred target of human collection. Because they are protandric species, selectively eliminating larger specimens of a given population seriously compromises their viability and has led to local extinction events in some cases. Additionally, sustained collection over time may lead to microevolutionary responses that result in genetic changes. The growing presence of artificial structures in coastal ecosystems may cause population fragmentation and isolation, limiting the genetic flow and dispersion capacity of many limpet species. However, when they are necessitated, artificial structures could be managed to establish marine artificial microreserves and contribute to the conservation of giant limpet species that naturally settle on them.

Coral reef fisheries depend on reef fish biomass to support ecosystem functioning and sustainable fisheries. Here, we evaluated coral reefs across 4,000 km of the Indonesian archipelago to reveal a large gradient of biomass, from 17,000 kg/ha. Trophic pyramids characterized by planktivore dominance emerged at high biomass, suggesting the importance of pelagic pathways for reef productivity. Total biomass and the biomass of most trophic groups were higher within gear restricted and no-take management, but the greatest biomass was found on unmanaged remote reefs. Within marine protected areas (MPAs), 41.6% and 43.6% of gear restricted and no-take zones, respectively, met a global biomass target of 500 kg/ha, compared with 71.8% of remote sites. To improve conservation outcomes for Indonesia's biodiverse and economically important coral reef fisheries, our results suggest to: (1) strengthen management within Indonesia's existing MPAs and (2) precautionarily manage remote reefs with high biomass.

Knowledge of the spatial distribution of fish assemblages biodiversity and structure is essential for prioritizing areas of conservation. Here we describe the biodiversity and community structure of demersal fish assemblages and their habitat along the northeast Brazilian coast by combining bottom trawl data and underwater footage. Species composition was estimated by number and weight, while patterns of dominance were obtained based on frequency of occurrence and relative abundance. A total of 7235 individuals (830 kg), distributed in 24 orders, 49 families and 120 species were collected. Community structure was investigated through clustering analysis and by a non-metric multidimensional scaling technique. Finally, diversity was assessed based on six indices. Four major assemblages were identified, mainly associated with habitat type and depth range. The higher values of richness were found in sand substrate with rocks, coralline formations and sponges (SWCR) habitats, while higher values of diversity were found in habitats located on shallow waters (10–30 m). Further, assemblages associated with sponge-reef formations presented the highest values of richness and diversity. In management strategies of conservation, we thus recommend giving special attention on SWCR habitats, mainly those located on depths between 30 and 60 m. This can be achieved by an offshore expansion of existing MPAs and/or by the creation of new MPAs encompassing those environments.